Systems and methods for lesion assessment

ABSTRACT

Ablation visualization and monitoring systems and methods are provided. In some embodiments, such methods comprise applying ablation energy to a tissue to form a lesion in the tissue, illuminating the tissue with a light to excite NADH in the tissue, wherein the tissue is illuminated in a radial direction, an axial direction, or both, monitoring a level of NADH fluorescence in the illuminated tissue to determine when the level of NADH fluorescence decreases from a base level in the beginning of the ablating to a predetermined lower level, and stopping ablation of the tissue when the level of NADH fluorescence reaches the predetermined lower level.

RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalApplication Ser. No. 62/074,619, filed on Nov. 3, 2014, which isincorporated herein by reference in its entirety.

FIELD

The present disclosure generally relates to ablation visualization andmonitoring systems and methods.

BACKGROUND

Atrial fibrillation (AF) is the most common sustained arrhythmia in theworld, which currently affects millions of people. In the United States,AF is projected to affect 10 million people by the year 2050. AF isassociated with increased mortality, morbidity, and an impaired qualityof life, and is an independent risk factor for stroke. The substantiallifetime risk of developing AF underscores the public heath burden ofthe disease, which in the U.S. alone amounts to an annual treatment costexceeding $7 billion.

Most episodes in patients with AF are known to be triggered by focalelectrical activity originating from within muscle sleeves that extendinto the Pulmonary Veins (PV). Atrial fibrillation may also be triggeredby focal activity within the superior vena cava or other atrialstructures, i.e. other cardiac tissue within the heart's conductionsystem. These focal triggers can also cause atrial tachycardia that isdriven by reentrant electrical activity (or rotors), which may thenfragment into a multitude of electrical wavelets that are characteristicof atrial fibrillation. Furthermore, prolonged AF can cause functionalalterations in cardiac cell membranes and these changes furtherperpetuate atrial fibrillation.

Radiofrequency ablation (RFA), laser ablation and cryo ablation are themost common technologies of catheter-based mapping and ablation systemsused by physicians to treat atrial fibrillation. Physicians use acatheter to direct energy to either destroy focal triggers or to formelectrical isolation lines isolating the triggers from the heart'sremaining conduction system. The latter technique is commonly used inwhat is called pulmonary vein isolation (PVI). However, the success rateof the AF ablation procedure has remained relatively stagnant withestimates of recurrence to be as high as 30% to 50% one-year postprocedure. The most common reason for recurrence after catheter ablationis one or more gaps in the PVI lines. The gaps are usually the result ofineffective or incomplete lesions that may temporarily block electricalsignals during the procedure but heal over time and facilitate therecurrence of atrial fibrillation.

PV isolation (PVI) can be accomplished in most patients using irrigatedablation catheters, however recurrence of AF may occur over time.Recurrences are thought to be due to PV reconnections from sites thateither recovered, gaps in the ablation lines, or ablated sites that didnot achieve transmurality during the initial procedure. Therefore,lesion assessment is very important in catheter ablation procedures sothat the operator can deliver the best possible lesions during pulmonaryvein isolation procedures. The improved quality of the lesions canreduce atrial fibrillation recurrences.

Real-time optical tissue characterization can provide excellent andpreviously impossible assessment of electrode-tissue contact and lesionprogression during ablation. It can also provide highly valuableinformation regarding the myocardium, collagen, elastin tissuecomposition at the site of catheter tip and represents a new frontier inthe understanding of the complex nature of the biophysics of cardiacablation. Lesion depth directly correlates to a decrease in fNADH signalintensity. This information should be used to optimize the selection ofablation power and ablation energy application time to maximize lesionformation and improve the success of ablation procedures. Therefore,there is a need for systems and methods for real-time optical tissuecharacterization.

SUMMARY

Ablation visualization and monitoring systems and methods are provided.

According to some aspects of the present disclosure, there is provided amethod that includes applying ablation energy to a tissue to form alesion in the tissue, illuminating the tissue with light energy (suchas, for example, UV light) to excite NADH in the tissue, wherein thetissue is illuminated in a radial direction, an axial direction, orboth, monitoring a level of NADH fluorescence in the illuminated tissueto determine when the level of NADH fluorescence decreases from a baselevel in the beginning of the ablating to a predetermined lower level,and stopping ablation of the tissue when the level of NADH fluorescencereaches the predetermined lower level.

According to some aspects of the present disclosure, there is provided asystem for monitoring tissue ablation that includes a cathetercomprising a catheter body and a distal tip positioned at a distal endof the catheter body, the distal tip defining an illumination cavityhaving one or more openings for exchange of light energy between theillumination cavity and tissue, an ablation system in communication withthe distal tip to deliver ablation energy to distal tip, a visualizationsystem comprising a light source, a light measuring instrument, and oneor more optical fibers in communication with the light source and thelight measuring instrument and extending through the catheter body intothe illumination cavity of the distal tip, wherein the one or moreoptical fibers are configured to pass light energy in and out of theillumination chamber, and a processor in communication with the ablationenergy source, light source and the light measuring instrument, theprocessor being programmed to collect light reflected from a tissueilluminated with light energy (such as, for example, UV light) to exciteNADH in the tissue, while ablation energy is being applied to the tissueto form a lesion in the tissue; monitor a level of NADH fluorescence inthe illuminated tissue to determine when the level of NADH fluorescencedecreases from a base level in the beginning of the ablating to apredetermined lower level; and cause ablation of the tissue to stop whenthe level of NADH fluorescence reaches the predetermined lower level.

BRIEF DESCRIPTION OF THE DRAWINGS

The presently disclosed embodiments will be further explained withreference to the attached drawings, wherein like structures are referredto by like numerals throughout the several views. The drawings shown arenot necessarily to scale, with emphasis instead generally being placedupon illustrating the principles of the presently disclosed embodiments.

FIG. 1A illustrates an embodiment of an ablation visualization andmonitoring system of the present disclosure.

FIG. 1B is a diagram of an embodiment of a visualization system for usein connection with an ablation visualization and monitoring system ofthe present disclosure.

FIG. 1C illustrates an exemplary computer system suitable for use inconnection with the systems and methods of the present disclosure.

FIGS. 2A-2E illustrate various embodiments of catheters of the presentdisclosure.

FIG. 3 illustrates exemplary fluorescence spectral plots for monitoringcontact between a catheter and tissue according to the presentdisclosure.

FIG. 4 illustrates exemplary spectral plots of various tissuecompositions.

FIG. 5 and FIG. 6 illustrate plots of fNADH over time during formationof endocardial lesions and epicardial lesions, respectively.

FIG. 7A, FIG. 7B and FIG. 7C illustrate exemplary fluorescence spectralplots for monitoring stability of a catheter according to the presentdisclosure.

FIG. 8A and FIG. 8B illustrate exemplary fNADH signal as the cathetertraverses from healthy tissue to the margin of a lesion and then to thecenter of a lesion.

FIG. 9 is a graph comparing fNADH and Impedance over time during anapplication of ablation energy.

While the above-identified drawings set forth presently disclosedembodiments, other embodiments are also contemplated, as noted in thediscussion. This disclosure presents illustrative embodiments by way ofrepresentation and not limitation. Numerous other modifications andembodiments can be devised by those skilled in the art which fall withinthe scope and spirit of the principles of the presently disclosedembodiments.

DETAILED DESCRIPTION

The present disclosure provides methods and systems for lesionassessment. In some embodiments, the system of the present disclosureincludes a catheter configured to serve two functions: a therapeuticfunction of delivering ablation therapy to a target tissue and adiagnostic function of gathering a signature spectrum from a point ofcontact of the catheter and tissue to access lesions. In someembodiments, the systems and methods of the present disclosure may beemployed for imaging tissue using nicotinamide adenine dinucleotidehydrogen (NADH) fluorescence (fNADH). In general, the system may includea catheter with an optical system for exchanging light between tissueand the catheter. In some embodiments, the instant systems allow fordirect visualization of the tissue's NADH fluorescence, or lack thereof,induced by ultraviolet (UV) excitation. The NADH fluorescence signaturereturned from the tissue can be used to determine the quality of contactbetween the tissue and a catheter system.

In some embodiments, the catheter includes an ablation therapy system atits distal end and is coupled to a diagnostic unit comprising a lightsource, such as a laser, and a spectrometer. The catheter may includeone or more fibers extending from the light source and the spectrometerto a distal tip of the catheter to provide illuminating light to thepoint of contact between the catheter and tissue and to receive anddeliver a signature NADH spectrum from the point of contact to thespectrometer. The signature NADH spectrum may be used to assess a lesionin the target tissue. In some embodiments, the methods of the presentdisclosure include illuminating a tissue having a lesion, receiving asignature spectrum of the tissue, and performing a qualitativeassessment of the lesion based on the signature spectrum from thetissue. The analysis can occur in real-time before, during and afterablation lesion formation. It should be noted that while the systems andmethods of the present disclosure are described in connection withcardiac tissue and NADH spectrum, the systems and methods of the presentdisclosure may be used in connection with other types of tissue andother types of fluorescence.

System: Diagnostic Unit

In reference to FIG. 1A, the system for providing ablation therapy 100may include an ablation therapy system 110, a visualization system 120,and a catheter 140. In some embodiments, the system 100 may also includeone or more of an irrigation system 170, ultrasound system 190 and anavigation system 200. The system may also include a display 180, whichcan be a separate display or a part of the visualization system 120, asdescribed below. In some embodiments, the system includes an RFgenerator, an irrigation pump 170, an irrigated-tip ablation catheter140, and the visualization system 120.

In some embodiments, the ablation therapy system 110 is designed tosupply ablation energy to the catheter 140. The ablation therapy system110 may include one or more energy sources that can generateradiofrequency (RF) energy, microwave energy, electrical energy,electromagnetic energy, cryoenergy, laser energy, ultrasound energy,acoustic energy, chemical energy, thermal energy or any other type ofenergy that can be used to ablate tissue. In some embodiments, thecatheter 140 is adapted for an ablation energy, the ablation energybeing one or more of RF energy, cryo energy, laser, chemical,electroporation, high intensity focused ultrasound or ultrasound, andmicrowave.

In reference to FIG. 1B, the visualization system 120 may include alight source 122, a light measuring instrument 124, and a computersystem 126.

In some embodiments, the light source 122 may have an output wavelengthwithin the target fluorophore (NADH, in some embodiments) absorptionrange in order to induce fluorescence in healthy myocardial cells. Insome embodiments, the light source 122 is a solid-state laser that cangenerate UV light to excite NADH fluorescence. In some embodiments, thewavelength may be about 355 nm or 355 nm+/−30 nm. In some embodiments,the light source 122 can be a UV laser. Laser-generated UV light mayprovide much more power for illumination and may be more efficientlycoupled into a fiber-based illumination system, as is used in someembodiments of the catheter 140. In some embodiments, the instant systemcan use a laser with adjustable power up to 150 mW.

The wavelength range on the light source 122 may be bounded by theanatomy of interest, or a user specifically choosing a wavelength thatcauses maximum NADH fluorescence without exciting excessive fluorescenceof collagen, which exhibits an absorption peak at only slightly shorterwavelengths. In some embodiments, the light source 122 has a wavelengthfrom 300 nm to 400 nm. In some embodiments, the light source 122 has awavelength from 330 nm to 370 nm. In some embodiments, the light source122 has a wavelength from 330 nm to 355 nm. In some embodiments, anarrow-band 355 nm source may be used. The output power of the lightsource 122 may be high enough to produce a recoverable tissuefluorescence signature, yet not so high as to induce cellular damage.The light source 122 may be coupled to an optical fiber to deliver lightto the catheter 140, as will be described below.

In some embodiments, the systems of the present disclosure may utilize aspectrometer as the light measuring instrument 124. In some embodiments,the light measuring instrument 124 may comprise a camera connected tothe computer system 126 for analysis and viewing of tissue fluorescence.In some embodiments, the camera may have high quantum efficiency forwavelengths corresponding to NADH fluorescence. One such camera is anAndor iXon DV860. The spectrometer 124 may be coupled to an imagingbundle that can be extended into the catheter 140 for visualization oftissue. In some embodiments, the imaging bundle for spectroscopy and theoptical fiber for illumination may be combined. An optical bandpassfilter of between 435 nm and 485 nm, in some embodiments, of 460 nm, maybe inserted between the imaging bundle and the camera to block lightoutside of the NADH fluorescence emission band. In other words, a filterhaving a center wavelength of 460 nm with a 50 nm bandwidth may beutilized. In some embodiments, other optical bandpass filters may beinserted between the imaging bundle and the camera to block lightoutside of the NADH fluorescence emission band selected according to thepeak fluorescence of the tissue being imaged.

In some embodiments, the light measuring instrument 124 may be a CCD(charge-coupled device) camera. In some embodiments, the spectrometer124 may be selected so it is capable of collecting as many photons aspossible and that contributes minimal noise to the image. Usually forfluorescence imaging of live cells, CCD cameras should have a quantumefficiency at about 460 nm of at least between 50-70%, indicating that30-50% of photons will be disregarded. In some embodiments, the camerahas quantum efficiency at 460 nm of about 90%. The camera may have asample rate of 80 KHz. In some embodiments, the spectrometer 124 mayhave a readout noise of 8 e− (electrons) or less. In some embodiments,the spectrometer 124 has a minimum readout noise of 3 e−. Other lightmeasuring instruments may be used in the systems and methods of thepresent disclosure.

The optical fiber can deliver the gathered light to a long pass filterthat blocks the reflected excitation wavelength of 355 nm, but passesthe fluoresced light that is emitted from the tissue at wavelengthsabove the cutoff of the filter. The filtered light from the tissue canthen be captured and analyzed by the light measuring instrument 124. Thecomputer system 126 acquires the information from the light measuringinstrument 124 and displays it to the physician.

In some embodiments, the digital image that is produced by analyzing thelight data may be used to do the 2D and 3D reconstruction of the lesion,showing size, shape and any other characteristics necessary foranalysis. In some embodiments, the image bundle may be connected to thelight measuring instrument 124, which may generate a digital image ofthe lesion being examined from NADH fluorescence (fNADH), which can bedisplayed on the display 180. In some embodiment, these images can bedisplayed to the user in real time. The images can be analyzed by usingsoftware to obtain real-time details (e.g. intensity or radiated energyin a specific site of the image) to help the user to determine whetherfurther intervention is necessary or desirable. In some embodiments, theNADH fluorescence may be conveyed directly to the computer system 126.

In some embodiments, the optical data acquired by the light measuringinstrument 124 can be analyzed to provide information about lesionsduring and after ablation including, but not limited to lesion depth andlesion size. In some embodiments, data from the light measuringinstrument can be analyzed to determine if the catheter 140 is incontact with the myocardial surface and how much pressure is applied tothe myocardial surface by the tip of the catheter. In some embodiments,data from the light measuring instrument 124 is analyzed to determinethe presence of collagen or elastin in the tissue. In some embodiments,data from the light measuring instrument is analyzed and presentedvisually to the user via a graphical user interface in a way thatprovides the user with real-time feedback regarding lesion progression,lesion quality, myocardial contact, tissue collagen content, and tissueelastin content.

In some embodiments, the system 100 of the present disclosure mayfurther include an ultrasound system 190. The catheter 140 may beequipped with ultrasound transducers in communication with theultrasound system 190. In some embodiments, the ultrasound may showtissue depths, which in combination with the metabolic activity or thedepth of lesion may be used to determine if a lesion is transmural ornot. In some embodiments, the ultrasound transducers may be located inthe distal section of the catheter 140, and optionally in the tip of thedistal electrode. The ultrasonic transducers may be configured to assessa tissue thickness either below or adjacent to the catheter tip. In someembodiments, the catheter 140 may comprise multiple transducers adaptedto provide depth information covering a situation where the catheter tipis relatively perpendicular to a myocardium or relatively parallel to amyocardium.

Referring back to FIG. 1A, as noted above, the system 100 may alsoinclude an irrigation system 170. In some embodiments, the irrigationsystem 170 pumps saline into the catheter 140 to cool the tip electrodeduring ablation therapy. This may help to prevent steam pops and char(i.e. clot that adheres to the tip that may eventually dislodge andcause a thrombolytic event) formation. In some embodiments, theirrigation fluid is maintained at a positive pressure relative topressure outside of the catheter 140 for continuous flushing of the oneor more openings 154.

Referring back to FIG. 1A, the system 100 may also include a navigationsystem 200 for locating and navigating the catheter 140. In someembodiments, the catheter 140 may include one or more electromagneticlocation sensors in communication with the navigation system 200. Insome embodiments, the electromagnetic location sensors may be used tolocate the tip of the catheter in the navigation system 200. The sensorpicks up electromagnetic energy from a source location and computeslocation through triangulation or other means. In some embodiments thecatheter 140 comprises more than one transducer adapted to render aposition of the catheter body 142 and a curvature of the catheter bodyon a navigation system display. In some embodiments, the navigationsystem 200 may include one or more magnets and alterations in themagnetic field produced by the magnets on the electromagnetic sensorscan deflect the tip of catheters to the desired direction. Othernavigation systems may also be employed, including manual navigation.

The computer system 126 can be programmed to control various modules ofthe system 100, including, for example, control over the light source122, control over the light measuring instrument 124, execution ofapplication specific software, control over ultrasound, navigation andirrigation systems and similar operations.

FIG. 1C shows, by way of example, a diagram of a typical processingarchitecture 308, which may be used in connection with the methods andsystems of the present disclosure. A computer processing device 340 canbe coupled to display 340AA for graphical output. Processor 342 can be acomputer processor 342 capable of executing software. Typical examplescan be computer processors (such as Intel® or AMD® processors), ASICs,microprocessors, and the like. Processor 342 can be coupled to memory346, which can be typically a volatile RAM memory for storinginstructions and data while processor 342 executes. Processor 342 mayalso be coupled to storage device 348, which can be a non-volatilestorage medium, such as a hard drive, FLASH drive, tape drive, DVDROM,or similar device. Although not shown, computer processing device 340typically includes various forms of input and output. The I/O mayinclude network adapters, USB adapters, Bluetooth radios, mice,keyboards, touchpads, displays, touch screens, LEDs, vibration devices,speakers, microphones, sensors, or any other input or output device foruse with computer processing device 340. Processor 342 may also becoupled to other type of computer-readable media, including, but are notlimited to, an electronic, optical, magnetic, or other storage ortransmission device capable of providing a processor, such as theprocessor 342, with computer-readable instructions. Various other formsof computer-readable media can transmit or carry instructions to acomputer, including a router, private or public network, or othertransmission device or channel, both wired and wireless. Theinstructions may comprise code from any computer-programming language,including, for example, C, C++, C#, Visual Basic, Java, Python, Perl,and JavaScript.

Program 349 can be a computer program or computer readable codecontaining instructions and/or data, and can be stored on storage device348. The instructions may comprise code from any computer-programminglanguage, including, for example, C, C++, C#, Visual Basic, Java,Python, Perl, and JavaScript. In a typical scenario, processor 204 mayload some or all of the instructions and/or data of program 349 intomemory 346 for execution. Program 349 can be any computer program orprocess including, but not limited to web browser, browser application,address registration process, application, or any other computerapplication or process. Program 349 may include various instructions andsubroutines, which, when loaded into memory 346 and executed byprocessor 342 cause processor 342 to perform various operations, some orall of which may effectuate the methods for managing medical caredisclosed herein. Program 349 may be stored on any type ofnon-transitory computer readable medium, such as, without limitation,hard drive, removable drive, CD, DVD or any other type ofcomputer-readable media.

In some embodiments, the computer system may be programmed to performthe steps of the methods of the present disclosure and control variousparts of the instant systems to perform necessary operation to achievethe methods of the present disclosure. In some embodiments, theprocessor may be programmed to collect light reflected from a tissueilluminated with a UV light to excite NADH in the tissue, while ablationenergy is being applied to the tissue to form a lesion in the tissue;monitor a level of NADH fluorescence in the illuminated tissue todetermine when the level of NADH fluorescence decreases from a baselevel in the beginning of the ablating to a predetermined lower level;and cause (either automatically or by prompting the user) ablation ofthe tissue to stop when the level of NADH fluorescence reaches thepredetermined lower level. In some embodiments, a spectrum offluorescence light (including, but not limited to, the NADHfluorescence) reflected from the illuminated tissue may be collected todistinguish tissue type. In some embodiments, the tissue is illuminatedwith light having a wavelength between about 300 nm and about 400 nm. Insome embodiments, a level of the reflected light having a wavelengthbetween about 450 nm and 470 nm is monitored. In some embodiments, themonitored spectrum may be between 410 nm and 520 nm. Additionally oralternatively, a wider spectrum may be monitored, such as, by way of anon-limiting example, between 375 nm and 575 nm. In some embodiments,the NADH fluorescence spectrum and a wider spectrum may be displayed touser simultaneously. In some embodiments, the lesion may be created byablation energy selected from the group consisting of radiofrequency(RF) energy, microwave energy, electrical energy, electromagneticenergy, cryoenergy, laser energy, ultrasound energy, acoustic energy,chemical energy, thermal energy and combinations thereof. In someembodiments, the processor may start (either automatically or byprompting the user) the procedure when a NADH fluorescence peak isdetected so it can be monitored throughout the procedure. As notedabove, these methods may be used in combination with other diagnosticmethods, such as ultrasound monitoring.

System: Catheter

The catheter 140 may be based on a standard ablation catheter withaccommodations for the optical fibers for illumination and spectroscopy,as discussed above. In some embodiments, the catheter 140 is asteerable, irrigated RF ablation catheter that can be delivered througha sheath to the endocardial space via a standard transseptal procedureand common access tools. On the handle of the catheter 147, there may beconnections for the standard RF generator and irrigation system 170 fortherapy. The catheter handle 147 also passes the optical fibers that arethen connected to the diagnostic unit to obtain the tissue measurements.

Referring back to FIG. 1A, the catheter 140 includes a catheter body 142having a proximal end 144 and a distal end 146. The catheter body 142may be made of a biocompatible material, and may be sufficientlyflexible to enable steering and advancement of the catheter 140 to asite of ablation. In some embodiments, the catheter body 142 may havezones of variable stiffness. For example, the stiffness of the catheter140 may increase from the proximal end 144 toward the distal end 146. Insome embodiments, the stiffness of the catheter body 142 is selected toenable delivery of the catheter 140 to a desired cardiac location. Insome embodiments, the catheter 140 can be a steerable, irrigatedradiofrequency (RF) ablation catheter that can be delivered through asheath to the endocardial space, and in the case of the heart's leftside, via a standard transseptal procedure using common access tools.The catheter 140 may include a handle 147 at the proximal end 144. Thehandle 147 may be in communication with one or more lumens of thecatheter to allow passage of instruments or materials through thecatheter 140. In some embodiments, the handle 147 may includeconnections for the standard RF generator and irrigation system 170 fortherapy. In some embodiments, the catheter 140 may also include one moreadaptors configured to accommodate the optical fiber for illuminationand spectroscopy.

In reference to FIG. 1A, at the distal end 146, the catheter 140 mayinclude a distal tip 148, having a side wall 156 and a front wall 158.The front wall 158 may be, for example, flat, conical or dome shaped. Insome embodiments, the distal tip 148 may be configured to act as anelectrode for diagnostic purposes, such as for electrogram sensing, fortherapeutic purposes, such as for emitting ablation energy, or both. Insome embodiments where ablation energy is required, the distal tip 148of the catheter 140 could serve as an ablation electrode or ablationelement.

In the embodiments where RF energy is implemented, the wiring to couplethe distal tip 148 to the RF energy source (external to the catheter)can be passed through a lumen of the catheter. The distal tip 148 mayinclude a port in communication with the one or more lumens of thecatheter. The distal tip 148 can be made of any biocompatible material.In some embodiments, if the distal tip 148 is configured to act as anelectrode, the distal tip 148 can be made of metal, including, but notlimited to, platinum, platinum-iridium, stainless steel, titanium orsimilar materials.

In reference to FIG. 2A, an optical fiber or an imaging bundle 150 maybe passed from the visualization system 120, through the catheter body142, and into an illumination cavity or compartment 152, defined by thedistal tip 148. The distal tip 148 may be provided with one or moreopenings 154 for exchange of light energy between the illuminationcavity 152 and tissue. In some embodiments, even with multiple openings154, the function of the distal tip 148 as an ablation electrode is notcompromised. The openings may be disposed on the front wall 156, on theside wall 158 or both. The openings 154 may also be used as irrigationports. The light is delivered by the fiber 150 to the distal tip 148,where it illuminates the tissue in the proximity of the distal tip 148.This illumination light is either reflected or causes the tissue tofluoresce. The light reflected by and fluoresced from the tissue may begathered by the optical fiber 150 within the distal tip 148 and carriedback to the visualization system 120. In some embodiments, the sameoptical fiber or bundle of fibers 150 may be used to both direct lightoutside the distal tip to illuminate tissue outside the catheter 140 andto collect light from the tissue.

In reference to FIG. 2A, in some embodiments, the catheter 140 may havea visualization lumen 161 through which the optical fiber 150 may beadvanced through the catheter body 142. The optical fiber 150 may beadvanced through the visualization lumen 161 into the illuminationcavity 152 to illuminate the tissue and receive reflected light throughthe opening 154. As necessary, the optical fiber 150 may be advancedbeyond the illumination cavity 152 through the opening 154.

As shown in FIG. 2A and FIG. 2B, in addition to the visualization lumen161, the catheter 140 may further include an irrigation lumen 163 forpassing irrigation fluid from the irrigation system 170 to the openings154 (irrigation ports) in the distal tip 148 and an ablation lumen 164for passing ablation energy from the ablation therapy system 110 to thedistal tip 148, such as, for example, by passing a wire through theablation lumen 164 for RF ablation energy. It should be noted that thelumens of the catheter may be used for multiple purposes and more thanone lumen may be used for the same purpose. In addition, while FIG. 2Aand FIG. 2B show the lumens being concentric other configurations oflumens may be employed.

As shown in FIG. 2A and FIG. 2B, in some embodiments, a central lumen ofthe catheter may be utilized as the visualization lumen 161. In someembodiments, as shown in FIG. 2C, the visualization lumen 161 may be offset in relation to the central access of the catheter 140.

In some embodiments, the light may also be directed radially out of theopenings 154 in the side wall 156, alternatively or additionally tobeing directed through the opening in the front wall 158. In thismanner, the light energy exchange between the illumination cavity 152and tissue may occur over multiple paths, axially, radially or both withrespect to the longitudinal central axis of the catheter, as shown inFIG. 2E. This is useful when the anatomy will not allow the catheter tipto be orthogonal to the target site. It may also be useful whenincreased illumination is required. In some embodiments, additionaloptical fibers 150 may be used and may be deflected in the radialdirection with respect to the catheter 140 to allow the illumination andreturned light to exit and enter along the length of the catheter.

In reference to FIG. 2D, to enable the light energy exchange between theillumination cavity 152 and tissue over multiple paths (axially andradially with respect to the longitudinal central axis of the catheter),a light directing member 160 may be provided in the illumination cavity152. The light directing member 160 may direct the illumination light tothe tissue and direct the light returned through the one or moreopenings 154 within the distal tip 148 to the optical fiber 150. Thelight directing member 160 may also be made from any biocompatiblematerial with a surface that reflects light or can be modified toreflect light, such as for example, stainless steel, platinum, platinumalloys, quartz, sapphire, fused silica, metallized plastic, or othersimilar materials. The light directing member 160 may be conical (i.e.smooth) or faceted with any number of sides. The light directing member160 may be shaped to bend the light at any desired angle. In someembodiments, the light directing member 160 may be shaped to reflect thelight only through the one or more openings. In some embodiments, thematerial for the light directing member 160 is chosen from materialsthat do not fluoresce when exposed to illumination between 310 nm to 370nm. In some embodiments, as shown in FIG. 2D, the light directing member160 may include one or more holes 162 through the centerline of themirror, which allow illumination and reflected light to pass in bothdirections axially, directly in line with the catheter 140. Such anaxial path may be useful when the distal-most surface of the distal tip148 is in contact with the anatomy. The alternate radial paths, as shownin FIG. 2E, may be useful when the anatomy will not allow thedistal-most surface of the distal tip 148 to be in contact with thetarget site as is sometimes the case in the left atrium of the patientduring pulmonary vein isolation procedures, common in treating atrialfibrillation. In some embodiments, in all pathways, lensing may not berequired and the optical system is compatible with the irrigation system170 as the light passes through the cooling fluid, which is oftensaline. The irrigation system 170 may also serve to flush the blood fromthe holes 162, thus keeping the optical components clean.

Methods of Use

In some embodiments, methods for monitoring tissue ablation areprovided. Such methods may provide a real time visual feedback onvarious factors that can impact lesion formation by displaying the levelof NADH fluorescence, as is described below.

In some embodiments, the methods include applying ablation energy to atissue to form a lesion in the tissue, illuminating the tissue with UVlight to excite NADH in the tissue, wherein the tissue is illuminated ina radial direction, an axial direction, or both, monitoring a level ofNADH fluorescence in the illuminated tissue to determine when the levelof NADH fluorescence decreases from a base level in the beginning of theablating to a predetermined lower level, and stopping ablation of thetissue when the level of NADH fluorescence reaches the predeterminedlower level. In some embodiments, a spectrum of fluorescence light(including, but not limited to, the NADH fluorescence) reflected fromthe illuminated tissue may be collected to distinguish tissue type. Insome embodiments, the tissue is illuminated with light having awavelength between about 300 nm and about 400 nm. In some embodiments, alevel of the reflected light having a wavelength between about 450 nmand 470 nm is monitored. In some embodiments, the monitored spectrum maybe between 410 nm and 520 nm. Additionally or alternatively, a widerspectrum may be monitored, such as, by way of a non-limiting example,between 375 nm and 575 nm. In some embodiments, the lesion may becreated by ablation energy selected from the group consisting ofradiofrequency (RF) energy, microwave energy, electrical energy,electromagnetic energy, cryoenergy, laser energy, ultrasound energy,acoustic energy, chemical energy, thermal energy and combinationsthereof. In some embodiments, the methods may be started when a NADHfluorescence peak is detected so it can be monitored throughout theprocedure. As noted above, these methods may be used in combination withother diagnostic methods, such as ultrasound monitoring.

Pre-Lesion Anatomical Assessment

Illumination of cardiac tissue at wavelengths of about 350 to about 360nm can elicit an auto-fluorescence response from NADH present in themitochondria of myocardial cells. Variability of myocardial fNADHresponse can indicate that the catheter is positioned against tissue. Insome embodiments, the entire spectral signature can be captured from 350nm to 850 nm range, or as shown in FIG. 3 from 400 to 700 nm, with thepeak fluorescence of NADH occurring around 460 nm. The blood in thecirculatory systems is capable of absorbing the light and therefore nofluorescence can be detected while the catheter is in the blood pool,which would indicate no contact between the catheter and the tissue. Asthe catheter touches the myocardium a characteristic tissue fluorescencespectral signature is elicited, which would indicate good contactresponse. On the other hand, if the catheter is pushed with excessiveforce to cause tenting, the transient ischemia can result in an elevatedfluorescence and the spectral signature shifts above the baseline. Theuse of such feedback may help reduce the risk of perforation duringcatheter ablation and manipulation, will help avoid ablation atsub-optimal tissue contact sites and hence decrease RF ablation time

Lesion Formation Assessment

The information content of the returned spectrum may be obtained inreal-time during lesion formation. The analysis and display of thespectrum can add qualitative assessment of the lesion, as it forms inreal-time. FIG. 4 shows the returned spectrum from an illuminationsource of 355 nm during lesion formation. The fNADH peak is betweenabout 450 nm and 550 nm. During ablation, the magnitude of the returnedspectrum between approximately 450 nm and 550 nm drops significantlyover time as the successful lesion forms. This effect is due to thereduction of metabolic activity and hence reduction of fNADH as thecells are ablated. This drop may be used as an indication when to stopablation. In some embodiments, the ablation may be stopped uponreduction in the fNADH signal by 80% or more. In some embodiments,reduction in fNADH signal by over 50% and resultant achievement ofsteady state fNADH signal for more than a specific period of time suchas 5 or 10 seconds may be used as a stopping point. In some embodiments,60% or more reduction in fNADH signal over a specific period of timesuch as up to 10 seconds and resultant steady state fNADH signal formore than 5 seconds may be used.

In reference to FIG. 4, in some embodiments, the spectral signature maybe collected over a broader spectrum. For example, the spectral patternof collagenous tissue is different than the one seen on healthymyocardium. The peak of the spectrum shifts to the left when imagingover collagenous tissue. This may be used by the user to identify thearea that is being treated as being mostly myocardium or being coveredby collagen, which is harder to ablate.

FIG. 5 and FIG. 6 also illustrate this phenomenon during successful RFlesion formation on endocardial and epicardial surfaces respectively. Inboth sets of plots, the peak magnitude of the wavelengths that correlateto fNADH (450 nm to 470 nm) are normalized and plotted versus ablationtime. As can be seen in FIG. 5, showing samples L4, L8, L30, L31, L32,and L33, there is a precipitous drop in the peak magnitude within thefirst 10 seconds and a continued low level through the duration of theapplication of energy to the endocardium. FIG. 6 shows the same plotwith samples L13, L14, L15, L16, L17, L18, L19, L21, L22, and L23 butwith the RF energy applied to the epicardium. Again the effect issimilar in both figures showing that the present systems and methods canbe beneficial to technologies that ablate arrhythmias from eithersurface of the heart. This could be significant in that the lesion maybe well formed in less time than originally thought and that continuedapplication of energy could be excessive (see the discussion belowregarding impedance). It has been well documented in the literature thatexcessive ablation energy to the blood pool or the tissue or both canlead to dramatically negative outcomes and procedural complications suchas intracardiac steam pops, endocardial crater formation (endocardialdenudation of the inner lining of the heart), thrombus (clot) formation,embolism (migration of clots), stroke, and even death. The ability tolimit energy delivery while ensuring optimal or even adequate lesion isthus beneficial in cardiac ablation.

In reference to FIG. 7A, FIG. 7B and FIG. 7C, in some embodiments, thespectral signature may be monitored to determine catheter stabilityduring lesion formation. For example, as shown in FIG. 7A, a smoothresponse corresponds to a stable catheter, as the gradual reduction infNADH intensity indicates the formation of the ablation lesion overtime. FIG. 7B shows a sharper, more noisy response, which corresponds tointermittent or shifting tip of the catheter in relation to tissue. FIG.7C shows that catheter movement can also be picked up during ablationbased on the fNADH, a transient shift in fNADH is seen when the catheterjumps to a different location.

Post-Lesion Anatomical Assessment

Finally, the ability to interrogate tissue to identify areas of poorablation or inadequate lesion formation, namely residual gaps andelectrically conducting zones, is a challenge in today's ablationparadigm. It is only feasible electrically with multiple catheters andis time consuming, laborious and utilizes considerable fluoroscopy(x-ray radiation exposure). This system can optically and visuallyidentify gaps without electrical interrogation yielding faster, saferand better identification of areas that were missed in a previousablation. This has significant implications in both acute procedures aswell as repeat ablations, or cases of previously failed ablationprocedures.

FIG. 8A and FIG. 8B show how the systems and methods of the presentdisclosure can be used to evaluate previously formed lesions, whetherthey are chronic or freshly made. FIG. 8A shows a sequential schematicrepresentation of a catheter tip as it moves from healthy myocardium tothe margin of an existing lesion and then over the center of theexisting lesion. FIG. 8B shows a composite of the normalized peakmagnitude of the optical spectrum returned under 355 nm illumination.The wavelengths central to fNADH has a significant difference in signalamplitude correlating perfectly to the state of the myocardium incontact with the tip of the catheter.

Comparison to Impedance

By way of a non-limiting example, FIG. 9 contrasts the fNADH responseand therapy impedance over the duration of lesion formation. Impedanceis a standard indicator used during ablation procedures throughout theworld. It is typically measured from the tip of the catheter to theablation ground pad adhered to the patient's torso. Physicians expect tosee a drop of approximately 10 to 15 ohms in the first 2 or 3 secondsafter the onset of ablation energy. If the impedance does not drop, thephysician knows that this is likely due to poor catheter contact withthe myocardium and the lesion attempt is aborted and the catheterrepositioned. The methods described above may be used to ensure bettercontact between the catheter and the tissue. If the impedance does dropand maintain a new level, the physician continues applyinglesion-forming energy typically for a fixed time (30 to 60 seconds ormore). If the impedance rises over time, it is an indicator of potentialoverheating at the tip of the catheter and if unabated can result indangerous situations of steam formation resulting in cardiac wallrupture or char buildup on the tip of the catheter that could dislodgeand become an embolic body.

As shown in FIG. 9, the signal-to-noise ratio (SNR) of the fNADH opticalresponse as compared to therapy impedance SNR would suggest that fNADHis a good indicator of lesion-formation quality. The change in amplitudeof the fNADH magnitude is approximately 80% where the same drop innormalized impedance is less than 10%. This comparison of opticalsignature to impedance also indicates a more direct reflection of theactivity in the tissue relative to impedance since the impedance oftenis a much larger reflection of the electrical path from the electrode tothe ground pad through the blood pool. Using the optical approach, allof the light signature is from the tissue and none originates from theblood pool if good contact is maintained. As such, the optical signatureis much more highly reflective of the activity in the tissue than theimpedance signature.

The foregoing disclosure has been set forth merely to illustrate variousnon-limiting embodiments of the present disclosure and is not intendedto be limiting. Since modifications of the disclosed embodimentsincorporating the spirit and substance of the disclosure may occur topersons skilled in the art, the presently disclosed embodiments shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof. All references cited in this applicationare incorporated herein by reference in their entireties.

What is claimed is:
 1. A method for monitoring ablation of cardiactissue of endocardium comprising: applying ablation energy to a cardiactissue to form a lesion in the tissue; illuminating the cardiac tissueto excite nicotinamide adenine dinucleotide hydrogen (NADH) in thecardiac tissue and determining a base level of NADH fluorescence in theilluminated cardiac tissue; monitoring a level of NADH fluorescence inthe illuminated cardiac tissue during the application of ablation energyto the illuminated cardiac tissue; reducing the NADH fluorescence in theilluminated cardiac tissue to between 60% and 80% of the base level andachieving a steady state NADH fluorescence; and upon achieving thesteady state NADH fluorescence for between 5 and 10 seconds, stoppingablation of the illuminated cardiac tissue to limit an amount ofablation energy delivered to the cardiac tissue.
 2. The method of claim1 wherein the cardiac tissue is illuminated with light having awavelength between about 300 nm and about 400 nm.
 3. The method of claim1 further comprising monitoring a level of the reflected light having awavelength between about 450 nm and 470 nm.
 4. The method of claim 1wherein the ablation energy is selected from the group consisting ofradiofrequency (RF) energy, microwave energy, electrical energy,electromagnetic energy, cryoenergy, laser energy, ultrasound energy,acoustic energy, chemical energy, thermal energy, electroporationenergy, and combinations thereof.
 5. The method of claim 1 furthercomprising advancing a catheter to the cardiac tissue, the cathetercomprising: a catheter body; a distal tip positioned at a distal end ofthe catheter body for delivering ablation energy to the cardiac tissue,the distal tip defining an illumination cavity having one or moreopenings for exchange of light between the illumination cavity and thetissue; and one or more optical fibers extending through the catheterbody into the illumination cavity of the distal tip, the one or moreoptical fibers being in communication with a light source and a lightmeasuring instrument to illuminate the cardiac tissue and to relay lightenergy reflected from the cardiac tissue to the light measuringinstrument.
 6. The method of claim 1 further comprising illuminating thecardiac tissue in a radial direction and an axial direction with respectto a longitudinal axis of a catheter.
 7. The method of claim 1 furthercomprising providing a real time visual feedback about the lesionformation by displaying the level of NADH fluorescence.
 8. The method ofclaim 1, wherein the ablation energy is applied when a NADH fluorescencepeak is detected.
 9. The method of claim 1 further comprising performingan ultrasound evaluation of cardiac tissue in combination withmonitoring the level of NADH fluorescence.
 10. The method of claim 1further comprising monitoring a level of the reflected light having awavelength between about 375 nm and about 575 nm.
 11. The method ofclaim 1, further comprising determining a proper position of a catheterfor applying ablation energy such that the catheter is positionedadjacent to the cardiac tissue, the proper position being determinedusing base level NADH fluorescence with NADH fluorescence above the baselevel indicating that the catheter is pushing on the cardiac tissue withexcessive force and NADH fluorescence below the base level indicatingthat the catheter is positioned in a blood pool and not adjacent thecardiac tissue.
 12. A system for monitoring tissue ablation comprising:a catheter comprising: a catheter body; and a distal tip positioned at adistal end of the catheter body, the distal tip having one or moreopenings for passing light energy to a cardiac tissue of endocardium; anablation system in communication with the distal tip to deliver ablationenergy to the distal tip; a visualization system comprising a lightsource, a light measuring instrument, and one or more optical fibers incommunication with the light source and the light measuring instrumentand extending through the catheter body to the distal tip, wherein theone or more optical fibers are configured to pass light energy to thecardiac tissue to illuminate the cardiac tissue to excite NADH in thecardiac tissue; a processor in communication with the light measuringinstrument, the processor being programmed to: determine a base level ofNADH fluorescence in the illuminated cardiac tissue; monitor a reductionin the NADH fluorescence in the illuminated cardiac tissue to between60% and 80% of the base level and a steady state NADH fluorescence; andwherein, upon achieving the steady state NADH fluorescence for between 5and 10 seconds, ablation of the illuminated cardiac tissue stops tolimit an amount of ablation energy delivered to the cardiac tissue. 13.The system of claim 12 wherein the cardiac tissue is illuminated withlight having a wavelength between about 300 nm and about 400 nm.
 14. Thesystem of claim 12 wherein the processor monitors a level of thereflected light having a wavelength between about 450 nm and about 470nm.
 15. The system of claim 12 wherein the ablation energy is selectedfrom the group consisting of radiofrequency (RF) energy, microwaveenergy, electrical energy, electromagnetic energy, cryoenergy, laserenergy, ultrasound energy, acoustic energy, chemical energy, thermalenergy, electroporation energy, and combinations thereof.
 16. The systemof claim 12 wherein the catheter is configured to illuminate the cardiactissue in a radial direction and an axial direction with respect to alongitudinal axis of the catheter.
 17. The system of claim 12 furthercomprising an irrigation system for irrigation of the one or moreopenings.
 18. The system of claim 12 wherein the catheter furthercomprises one or more ultrasound transducers and one or moreelectromagnetic location sensors and the system further comprises anultrasound system in communication with the one or more ultrasoundtransducers for ultrasound evaluation of the cardiac tissue.
 19. Thesystem of claim 12 wherein the catheter further includes one or moreelectromagnetic location sensors and the system further includes anavigation system in communication with the one or more electromagneticlocation sensors for locating and navigating the catheter.
 20. Thesystem of claim 12 wherein the system applies the ablation energy when aNADH fluorescence peak is detected.
 21. A system for monitoring tissueablation comprising: an elongated body; an ablation system associatedwith a distal tip of the elongated body for delivering ablation energyto cardiac tissue of endocardium; a visualization system comprising alight source, a light measuring instrument, and one or more opticalfibers in communication with the light source and the light measuringinstrument and extending through the elongated body to the distal tip,wherein the one or more optical fibers are configured to pass lightenergy to the cardiac tissue to illuminate the cardiac tissue to exciteNADH in the illuminated cardiac tissue; a processor in communicationwith the light measuring instrument, the processor being programmed to:determine a base level of NADH fluorescence in the illuminated cardiactissue; monitor a reduction in the NADH fluorescence in the illuminatedcardiac tissue to between 60% and 80% of the base level and a steadystate NADH fluorescence; and wherein, upon achieving the steady stateNADH fluorescence for between 5 and 10 seconds, ablation of theilluminated cardiac tissue is stopped to limit an amount of ablationenergy delivered to the cardiac tissue.
 22. The system of claim 21wherein the ablation energy is selected from the group consisting ofradiofrequency (RF) energy, microwave energy, electrical energy,electromagnetic energy, cryoenergy, laser energy, ultrasound energy,acoustic energy, chemical energy, thermal energy, electroporation energyand combinations thereof.
 23. The system of claim 21 wherein the cardiactissue is illuminated with light having a wavelength between about 300nm and about 400 nm.
 24. The system of claim 21 wherein the processormonitors a level of the reflected light having a wavelength betweenabout 450 nm and about 470 nm.
 25. The system of claim 21 wherein theprocessor monitors a level of the reflected light having a wavelengthbetween about 375 nm and about 575 nm.
 26. The system of claim 21further comprising an irrigation system associated with the distal tipof the elongated body.
 27. The system of claim 21 further comprising aballoon disposed at the distal tip of the elongated body.
 28. A systemfor monitoring-tissue ablation comprising: an elongated body having adistal tip; an ablation system for delivering electroporation energy tocardiac tissue of endocardium; a visualization system comprising a lightsource, a light measuring instrument, and one or more optical fibers incommunication with the light source and the light measuring instrumentand extending through the elongated body to the distal tip, wherein theone or more optical fibers are configured to pass light energy to thecardiac tissue to illuminate the cardiac tissue to excite NADH in theilluminated cardiac tissue; a processor in communication with the lightmeasuring instrument, the processor being programmed to: determine abase level of NADH fluorescence in the illuminated cardiac tissue;monitor a reduction in the NADH fluorescence in the illuminated cardiactissue to between 60% and 80% of the base level and a steady state NADHfluorescence; and wherein, upon achieving the steady state NADHfluorescence for between 5-10 seconds, ablation of the illuminatedcardiac tissue stops to limit an amount of ablation energy delivered tothe cardiac tissue.
 29. A method for treating atrial fibrillation ofcardiac tissue of endocardium comprising: applying ablation energy to acardiac tissue using an ablation catheter to form a lesion in the tissueat a location determined to treat atrial fibrillation; illuminating thecardiac tissue to excite NADH in the cardiac tissue and determining abase level of NADH fluorescence in the illuminated cardiac tissue;monitoring a level of NADH fluorescence in the illuminated cardiactissue during the application of ablation energy to the illuminatedcardiac tissue; stopping ablation of the illuminated cardiac tissue whenthe NADH fluorescence in the illuminated cardiac tissue reaches areduction from the base level between 60% and 80% and achieves a steadystate NADH fluorescence for a period of time between 5-10 seconds tolimit an amount of ablation energy delivered to the cardiac tissue. 30.The method of claim 29, further comprising interrogating the cardiactissue to confirm adequate ablation at the location of the lesion tochange electrical signals in the cardiac tissue to treat atrialfibrillation by identifying areas of the cardiac tissue with inadequatelesion formation using NADH fluorescence as the catheter is moved alonga surface of the cardiac tissue.
 31. A system for treating atrialfibrillation using tissue ablation comprising: an elongated body; anablation system associated with a distal tip of the elongated body fordelivering ablation energy to cardiac tissue of endocardium to treatatrial fibrillation; a visualization system comprising a light source, alight measuring instrument, and one or more optical fibers incommunication with the light source and the light measuring instrumentand extending through the elongated body to the distal tip, wherein theone or more optical fibers are configured to pass light energy to thecardiac tissue to illuminate the cardiac tissue to excite NADH in theilluminated cardiac tissue and to relay light energy reflected from thecardiac tissue to the light measuring instrument; a processor incommunication with the light measuring instrument, the processor beingprogrammed to: determine a base level of NADH fluorescence in theilluminated cardiac tissue; monitor a level of NADH fluorescence in theilluminated cardiac tissue during the application of ablation energy tothe illuminated cardiac tissue, wherein ablation of the illuminatedcardiac tissue is stopped when the NADH fluorescence in the illuminatedcardiac tissue reaches a reduction from the base level between 60% and80% and achieves a steady state NADH fluorescence for a period of timebetween 5-10 seconds to limit an amount of ablation energy delivered tothe cardiac tissue.
 32. The system of claim 31, wherein the distal tipof the elongated body is configured to interrogate the cardiac tissue toconfirm adequate ablation to change electrical signals in the cardiactissue to treat atrial fibrillation by identifying areas of the cardiactissue with inadequate lesion formation using NADH fluorescence as thedistal tip of the elongated body is moved along a surface of the cardiactissue.
 33. A system for treating atrial fibrillation using tissueablation comprising: an elongated body having a distal tip; an ablationsystem for delivering electroporation energy to cardiac tissue ofendocardium to treat atrial fibrillation; a visualization systemcomprising a light source, a light measuring instrument, and one or moreoptical fibers in communication with the light source and the lightmeasuring instrument and extending through the elongated body to thedistal tip, wherein the one or more optical fibers are configured topass light energy to the cardiac tissue to illuminate the cardiac tissueto excite NADH in the illuminated cardiac tissue and to relay lightenergy reflected from the cardiac tissue to the light measuringinstrument; a processor in communication with the light measuringinstrument, the processor being programmed to: determine a base level ofNADH fluorescence in the illuminated cardiac tissue; monitor a level ofNADH fluorescence in the illuminated cardiac tissue during theapplication of ablation energy to the illuminated cardiac tissue,wherein ablation of the illuminated cardiac tissue is stopped when theNADH fluorescence in the illuminated cardiac tissue reaches a reductionfrom the base level between 60% and 80% and achieves a steady state NADHfluorescence for a period of time between 5-10 seconds to limit anamount of ablation energy delivered to the cardiac tissue.
 34. Thesystem of claim 33, wherein the distal tip of the elongated body isconfigured to interrogate the cardiac tissue to confirm adequateablation to change electrical signals in the cardiac tissue to treatatrial fibrillation by identifying areas of the cardiac tissue withinadequate lesion formation using NADH fluorescence as the distal tip ofthe elongated body is moved along a surface of the cardiac tissue.